Since theres nowhere to find this manual on the internet, here it is if you have one of these detectors if you want to wire it up to your system.
Any idea what kind of horn it has?
It has no horn built in.
So you could put any horn or siren with a matching voltage?
There’s a normally open relay (the grey and orange wires) which is a switch contact and as long if it’s 12v it should be fine.